Carburetor overhaul

[Timothy B.]

Snowing hard today in Bel Air Md., the only time I remember this much snow was when I was a kid and we walked to school through two-three feet.

I wanted to post some pics of the Carter I am working on to show throttle shaft bushings and tool to install. The base has some damage from the hot slot and that's what the JB weld is there to repair. Carburetor ran good but air leaks from, well lets just say it is wore out..

[Christopher R.]

Re: Carburetor overhaul

Can you post some information on that tool? Source and price? What's it do?

How are you repairing worn throttle shafts?

[Stuart F.]

Re: Carburetor overhaul

Tim;

I feel for ya man, but I must admit not too much. We're suffering in 40 to 50 degree cold down here in Florida, but with sun most days and a little rain off and on. This has been our coldest winter since we moved here in 04. I do wish you'd keep that stuff (cold) all up country where it belongs. (just pulling your leg).

That kind of damage sort of tells me that carb was used on a cast iron manifold with exhaust heat passages, perhaps w/o the proper base gasket, phenolic spacer and SS plate. Too bad. I hate to see a good AFB suffer so much. I'm sure you have it well on the way to recovery - and the time to carry out the repairs. Based on mileage, what would you say it takes to wear the shaft bores to the point where it affects the carbs operation, i.e. vacuum leakage?

Stu Fox

[Timothy B.]

Re: Carburetor overhaul

Christopher and Stu, The damage to this carburetor is not as bad as the unsanded epoxy looks. I will post a pic of the sanded base tomorrow to show how the repair came out. I used JB weld because it's supposed to be good to 500* and compatible with aluminum..

Some carburetor rebuilders say on most carburetors installing bushings is overkill. These shafts did not fit snug when new and some of the machining on these carburetors leaves much to be desired. I have a 3721 that when the well was drilled from the main jet to primary venturi the hole just cut slightly into the primary throttle shaft bore so vacuum sucked gasoline through the shaft into the engine.

Christopher, the bushing repair is made with 3/8" bronze valve guide bushings and the drill has a small pilot to aid in centering the hole. I think there are better drills with longer pilot ends that extend the complete length through the shaft to keep both sides straight. I am very careful drilling and have a .375 (3/8") hone to make things smooth if needed.

The AFB's primary and secondary shaft bores have a larger hole that extends about half way in and the smaller hole for the shaft diameter the last inch or so. If you look closely at the pic you can see where I left about 1/16" inside to serve as a stop for the bushing. Everything fits nice but the shaft is not floppy loose like it was before, not tight either.

On the secondary shaft, it's really not wore bad but the blades will move up/down because like I said these things were not tight when made. There is no room to drill the secondary hole because it's to close to the float bowl. There is also a larger bore hole towards the outside then smaller bore for the shaft the last 1/2" or so. What I did here is to install teflon shaft bearings from holley secondary shafts. After cut to fit around the shaft, they slid in the outside bore with the shaft and fit perfect. The shaft opens and closed on the teflon and everything is centered. No drilling or any other change to secondary. I will post pics of this also.

Sorry for the long winded post, I don't want to shovel snow.. You guys should see all this snow, I am worried about roofs.

[Jim T.]

Re: Carburetor overhaul

Christopher and Stu, The damage to this carburetor is not as bad as the unsanded epoxy looks. I will post a pic of the sanded base tomorrow to show how the repair came out. I used JB weld because it's supposed to be good to 500* and compatible with aluminum..

Some carburetor rebuilders say on most carburetors installing bushings is overkill. These shafts did not fit snug when new and some of the machining on these carburetors leaves much to be desired. I have a 3721 that when the well was drilled from the main jet to primary venturi the hole just cut slightly into the primary throttle shaft bore so vacuum sucked gasoline through the shaft into the engine.

Christopher, the bushing repair is made with 3/8" bronze valve guide bushings and the drill has a small pilot to aid in centering the hole. I think there are better drills with longer pilot ends that extend the complete length through the shaft to keep both sides straight. I am very careful drilling and have a .375 (3/8") hone to make things smooth if needed.

The AFB's primary and secondary shaft bores have a larger hole that extends about half way in and the smaller hole for the shaft diameter the last inch or so. If you look closely at the pic you can see where I left about 1/16" inside to serve as a stop for the bushing. Everything fits nice but the shaft is not floppy loose like it was before, not tight either.

On the secondary shaft, it's really not wore bad but the blades will move up/down because like I said these things were not tight when made. There is no room to drill the secondary hole because it's to close to the float bowl. There is also a larger bore hole towards the outside then smaller bore for the shaft the last 1/2" or so. What I did here is to install teflon shaft bearings from holley secondary shafts. After cut to fit around the shaft, they slid in the outside bore with the shaft and fit perfect. The shaft opens and closed on the teflon and everything is centered. No drilling or any other change to secondary. I will post pics of this also.

Sorry for the long winded post, I don't want to shovel snow.. You guys should see all this snow, I am worried about roofs.

Here is a roof collapse that cost some money

https://www.thekathrynreport.com/.../dulles-airport-hangar-roof-collapse.html

[Stuart F.]

Re: Carburetor overhaul

Tim;

I have lived through a bad winter in Chicago years back where we didn't know where to put the next shovel full. Everyone was worried about their roofs. Generally, if you have a good pitch on it and there is not excess distance between supports, you will be fine. The garages that went down were old two car, shallow pitch (or flat), with little or no center supports. My neighbor, an elderly gentleman, was so concerned that he went out and tried to clear his house roof with a long handled pull scraper. He wrenched his back, went into the hospital for a back operation, and left out the back door in a box. I had advised him not to do it, but that if he insisted it needed to be done, to please let me and my son come over to help. He couldn't wait. We were clearing ours more for the concern of ice dam buildup at the eves as it was causing leaks during the day, i.e. water backing up under the shingles and leaking through the ceiling. That was a bad year alright, we all used poles with flags on the to find the driveways, and to locate fire hydrants. Had my first front wheel drive car that year and learned to appreciate them, but I still can't see buying such a car for just that feature - deep snow.

Stu Fox

[Timothy B.]

Re: Carburetor overhaul

Here are pics of the sanded damage to the bottom of the 3461. Also, you can see the teflon installed into the secondary throttle bores as I tried to describe above. This was done without any drilling because the outside first 3/4" of the hole is a larger diameter than the inside. It's just right for the teflon.

There is a pic of the inside showing how the teflon centered the shaft in the bore hole.

If anyone has a source for these throttle blade screws please let me know. I tried McMaster Carr but the head diameter will be to wide. I guess I could use them again but they have been out a few times in the past.